Mane Arati, Vidhate Pallavi, Kusro Chanchal, Waman Vaishali, Saxena Vandana, Kulkarni-Kale Urmila, Risbud Arun
National AIDS Research Institute, Pune, Maharashtra, India.
Savitribai Phule Pune University (Formerly University of Pune), Bioinformatics Centre, Pune, Maharashtra, India.
Mycoses. 2016 Feb;59(2):93-100. doi: 10.1111/myc.12439. Epub 2015 Dec 9.
Resistance to azole antifungals is a significant problem in Candida albicans. An understanding of resistance at molecular level is essential for the development of strategies to tackle resistance and rationale design of newer antifungals and target-based molecular approaches. This study presents the first evaluation of molecular mechanisms associated with fluconazole resistance in clinical C.albicans isolates from India. Target site (ERG11) alterations were determined by DNA sequencing, whereas real-time PCRs were performed to quantify target and efflux pump genes (CDR1, CDR2, MDR1) in 87 [Fluconazole susceptible (n = 30), susceptible-dose dependent (n = 30) and resistant (n = 27)] C.albicans isolates. Cross-resistance to fluconazole, ketoconazole and itraconazole was observed in 74.1% isolates. Six amino acid substitutions were identified, including 4 (E116D, F145L, E226D, I437V) previously reported ones and 2 (P406L, Q474H) new ones. CDR1 over-expression was seen in 77.7% resistant isolates. CDR2 was exclusively expressed with CDR1 and their concomitant over-expression was associated with azole cross-resistance. MDR1 and ERG11 over-expression did not seem to be associated with resistance. Our results show that drug efflux mediated by Adenosine-5'-triphosphate (ATP)-binding cassette transporters, especially CDR1 is the predominant mechanism of fluconazole resistance and azole cross-resistance in C. albicans and indicate the need for research directed towards developing strategies to tackle efflux mediated resistance to salvage azoles.
对唑类抗真菌药物耐药是白色念珠菌面临的一个重大问题。在分子水平上了解耐药性对于制定应对耐药性的策略、合理设计新型抗真菌药物以及基于靶点的分子方法至关重要。本研究首次对来自印度的临床白色念珠菌分离株中与氟康唑耐药相关的分子机制进行了评估。通过DNA测序确定靶点(ERG11)改变,同时进行实时PCR以定量87株[氟康唑敏感(n = 30)、剂量依赖敏感(n = 30)和耐药(n = 27)]白色念珠菌分离株中的靶点和外排泵基因(CDR1、CDR2、MDR1)。在74.1%的分离株中观察到对氟康唑、酮康唑和伊曲康唑的交叉耐药。鉴定出六个氨基酸取代,包括4个先前报道的(E116D、F145L、E226D、I437V)和2个新的(P406L、Q474H)。在77.7%的耐药分离株中观察到CDR1过表达。CDR2仅与CDR1共同表达,它们的同时过表达与唑类交叉耐药相关。MDR1和ERG11过表达似乎与耐药性无关。我们的结果表明,由三磷酸腺苷(ATP)结合盒转运蛋白介导的药物外排,尤其是CDR1,是白色念珠菌中氟康唑耐药和唑类交叉耐药的主要机制,并表明需要开展研究以制定应对外排介导的耐药性的策略,以挽救唑类药物。